Cine-Gamma VX2000 at DVinfo.net

Donnie Wagner · January 19th, 2005, 03:20 PM

The following quesiton was asked to a sony engineer...

Is there a way to hack a VX2000 to give it a "film-like" linear gamma curve. This is the response I got, through a forwarded email...

"The cine look you are attempting to achieve is done by shutting off the gamma correction and applying linear gain to the preamp section of the camera. Lifting the trace from the processor supplying gamma correction data to the preamps should do what you are asking."

I have not been able to get any further info from him. Any engineers or technical people out there wish to comment on this any further?

Mike Rehmus · January 19th, 2005, 03:36 PM

Couple of things:

1. Film does not have a linear gamma curve. It has knees at the high and low ends of the scale which is why people would like to have their CCD-based cameras emulate them.

2. If that engineer were found out by Sony, he'd never work there again.

3. It is pure speculation to discuss circuit changes unless you have some additional information about the active components in the system.

Far easier to emulate film in a Post operation, I'd think.

Donnie Wagner · January 21st, 2005, 04:30 PM

1. Correct, film does not have a linear gamma curve. But it is more linear that normal video- which has a large knee in the mid range, to help the average videographer who doesnt understand lighting.

2.(If that engineer were found out by Sony, he'd never work there again) Who cares?

3. Of course it's speculation. If I knew, I would'nt have posted the topic on a forum that is designed for people to share information and ask questions.

(Far easier to emulate film in a Post operation, I'd think.)

The goal is to increase the dynamic range, you can't do that in post.

Would anyone else like to comment.

Mike Rehmus · January 21st, 2005, 08:34 PM

<<<-- Originally posted by Donnie Wagner : 1. Correct, film does not have a linear gamma curve. But it is more linear that normal video- which has a large knee in the mid range, to help the average videographer who doesnt understand lighting.

2.(If that engineer were found out by Sony, he'd never work there again) Who cares?

We on this forum do care about people and posting that kind of information might get back to Sony.

3. Of course it's speculation. If I knew, I would'nt have posted the topic on a forum that is designed for people to share information and ask questions.

Sorry about the tone of my reply to that particular point. There is no information from Sony on the function of most of their circuits. The most anyone has been able to do in the past is hack the audio circuit of the cameras by bypassing the chip IIRC.

(Far easier to emulate film in a Post operation, I'd think.)
The goal is to increase the dynamic range, you can't do that in post.

The dynamic range cannot be affected by changing the curve mid-point. If you could employ a quieter video circuit between the CCD and the DSP, perhaps you could get some more range but I think the 8 bit DV spec will cap any increase to 256 levels, regardless of what you try to do. Of course you can compress a larger range into the 8 bits but that is self-defeating.

Would anyone else like to comment.

The lack of response is informative in this case I think. Had someone done this before, I think they would have posted about it. Mainly I think people selected another camera brand to get the modifiable gamma.

January 19th, 2005, 03:20 PM	#1
Donnie Wagner Regular Crew Join Date: Dec 2004 Location: Pittsburgh, PA Posts: 135	Cine-Gamma VX2000 The following quesiton was asked to a sony engineer... Is there a way to hack a VX2000 to give it a "film-like" linear gamma curve. This is the response I got, through a forwarded email... "The cine look you are attempting to achieve is done by shutting off the gamma correction and applying linear gain to the preamp section of the camera. Lifting the trace from the processor supplying gamma correction data to the preamps should do what you are asking." I have not been able to get any further info from him. Any engineers or technical people out there wish to comment on this any further?

January 19th, 2005, 03:36 PM	#2
Mike Rehmus Wrangler Join Date: May 2002 Location: Vallejo, California Posts: 4,049	Couple of things: 1. Film does not have a linear gamma curve. It has knees at the high and low ends of the scale which is why people would like to have their CCD-based cameras emulate them. 2. If that engineer were found out by Sony, he'd never work there again. 3. It is pure speculation to discuss circuit changes unless you have some additional information about the active components in the system. Far easier to emulate film in a Post operation, I'd think. __________________ Mike Rehmus Hey, I can see the carrot at the end of the tunnel!

January 21st, 2005, 04:30 PM	#3
Donnie Wagner Regular Crew Join Date: Dec 2004 Location: Pittsburgh, PA Posts: 135	Anyone Else? 1. Correct, film does not have a linear gamma curve. But it is more linear that normal video- which has a large knee in the mid range, to help the average videographer who doesnt understand lighting. 2.(If that engineer were found out by Sony, he'd never work there again) Who cares? 3. Of course it's speculation. If I knew, I would'nt have posted the topic on a forum that is designed for people to share information and ask questions. (Far easier to emulate film in a Post operation, I'd think.) The goal is to increase the dynamic range, you can't do that in post. Would anyone else like to comment.

January 21st, 2005, 08:34 PM	#4
Mike Rehmus Wrangler Join Date: May 2002 Location: Vallejo, California Posts: 4,049	Re: Anyone Else? <<<-- Originally posted by Donnie Wagner : 1. Correct, film does not have a linear gamma curve. But it is more linear that normal video- which has a large knee in the mid range, to help the average videographer who doesnt understand lighting. 2.(If that engineer were found out by Sony, he'd never work there again) Who cares? We on this forum do care about people and posting that kind of information might get back to Sony. 3. Of course it's speculation. If I knew, I would'nt have posted the topic on a forum that is designed for people to share information and ask questions. Sorry about the tone of my reply to that particular point. There is no information from Sony on the function of most of their circuits. The most anyone has been able to do in the past is hack the audio circuit of the cameras by bypassing the chip IIRC. (Far easier to emulate film in a Post operation, I'd think.) The goal is to increase the dynamic range, you can't do that in post. The dynamic range cannot be affected by changing the curve mid-point. If you could employ a quieter video circuit between the CCD and the DSP, perhaps you could get some more range but I think the 8 bit DV spec will cap any increase to 256 levels, regardless of what you try to do. Of course you can compress a larger range into the 8 bits but that is self-defeating. Would anyone else like to comment. The lack of response is informative in this case I think. Had someone done this before, I think they would have posted about it. Mainly I think people selected another camera brand to get the modifiable gamma. __________________ Mike Rehmus Hey, I can see the carrot at the end of the tunnel!